Ferguson has won 37 titles during his tenure at United, including 12 Premier League titles, two Champions League crowns and five FA Cups.

However, sports journalist Barclay believes Jose Mourinho's achievements of winning Champions Leagues with Porto and Inter Milan and league titles with Porto, Chelsea, Inter and Real Madrid in a shorter period of time, outstrips the Scotsman.

"In terms of achievements per year, Mourinho's done what Ferguson's done in about a third of the time," he said.

"Mourinho hasn't really had much more investment, if you adjust it for inflation. Remember, when Ferguson came to Manchester United he broke the British transfer record four times in his first six years. He would buy the obvious players from Roy Keane to Wayne Rooney, whoever was the best player in Britain.

"I doubt whether Mourinho would win as many trophies [in his career] as Ferguson but in terms of raw managerial talent I think Ferguson is behind Brian Clough and Mourinho, who is exceptional."

Mind games

Barclay believes Ferguson first realised he couldn't win any mind games with Mourinho when his United side fell 3-2 on aggregate to Porto in the Champions League in 2004.

"After the first time in 2004 when Ferguson tried to play a mind game on Porto and lost, since then there really weren't any mind game stuff between [Mourinho's] Chelsea and Manchester United," he said.

"Ferguson knows when he's beat. He knows Mourinho's a better manager than he is, one on one."

Check out the video above to hear more discussion on Ferguson and his relationship with Man City boss Roberto Mourinho.